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One thing I've learned over the years is if something bad happens during a restoration, it has happened to someone else before and that is what I'm hoping for by posting this thread. Please excuse me for a long post but more information is better than less.

The car: 1970 GT with 44K miles (documented) and everything related to the electrical system is original. Before this everything worked (except the clock of course). Before we go further the headlight wires are shot but they haven't shorted out (yet) and it has the original ignition switch but it was working OK before this.

The overview summary is I removed the instrument panel, installed a Retro Sound radio and replacement clock from OGTS, while there I replaced the indicator lights for good measure. After some mechanical repairs including the plastic heater control unit, reinstalling and powering up the fuel gauge refused to work and with the ignition in the on position and nothing else on the right hand parking/taillights were on but not the left. The turn signals did not work, neither left or right.

I started the engine and pulled up the headlights and all external lights came on, the fuel gauge still refused to respond ( it was working two days before and I tapped it with a screwdriver) but the other gauges seemed to be responding OK. Then I noticed white smoke coming from the general area of the parking light/dimmer switch panel and after pulling the lights down, shutting down the engine and disconnecting the battery I did what any level headed restorer does faced with this situation. I left the shop and poured myself 2 fingers of Jack figuring I'd hit it the next day.

Next day: Reconnected the battery (sparks showed a slight drain), switched the ignition to run, the discharge and oil pressure lights came on, the radio worked and the clock started to move. This time the right marker/taillights were not on. I tried the parking light switch and they all came on. It seemed all normal at this stage. I tried to start the engine and there was a muffled "click" from under the dash and all went dead. No lights, no power to the starter solenoid through the black red wire, radio dead - nothing.

The fuseable link at the starter is intact, I've got power to the fuse bock through the red/white wire. With the key in the run position there is no switched power to position 1 on the fuse block leading me to believe that the 50 year old ignition switch finally failed. I pulled the dash again (I'm getting really good at this now) and went through EVERY connection and ohmed out every ground and it all looks good. While the average wire resistance is high by today's standards (2.5 to 3.2 ohms) it is acceptable to 1970 standards. ALL connections are correct, at least according to wiring diagrams I have. I can find no visible evidence of overheating/shorting anywhere. The Parking light switch works, as does every other switch. The amp gauge is ok with 2.2 ohm resistance between the connectors.

The only way the right parking/tail light circuit could activate and not the left would be through a failed switch but it checks out OK. To add to that I did not touch anything to do with that circuit anyway. And what would link the fuel gauge to this weird failure? And why did the ignition work on Tuesday but not Wednesday?

I am a retired electronics engineer and this one has me stumped. Yes I could tear everything apart, replace everything and hope the anomaly goes away but I'm hoping somebody out there has had a similar experience and can point me into a solution.

Oh, BTW, I've read every thread on the web sight and I found nothing similar to this so thanks in advance if you have anything in mind that could help.
 

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Opel Key Master
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5,176 Posts
Couple of steps I would take next,
1st: bypass the ignition switch, put a crank trigger on the starter, with the key on crank it over and see if it starts. If it cranks and no start, see if your Coil is getting power on positive. If not jump it from power just for the time to test. It should start up
2nd if the coil did not get power, then yes you need to check the black wire from the ignition switch to see if you get power, if not, your switch is jacked

Start there and then report
 

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Just Some Dude in Jersey
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Before we go further the headlight wires are shot but they haven't shorted out (yet)

I started the engine and pulled up the headlights

AAAAAAAAAAAGGGGGGGGGHHHHHHH!

I almost coughed up my rectum when I read that. You're having electrical problems, you know your headlight wires are shot, and you're flipping your headlights.

AAAAAAAAAAAGGGGGGGGGHHHHHHH!

Okay, I did cough up my rectum that time.

I don't care if you buy a car with 10 miles on it, the FIRST thing you do to a GT is replace the headlight wires forward of the radiator wall. They are unfused. They are made of vinyl which dried out and turned to dust after just 10 years. These are 50 year old cars. I had GT's in the early 80's that when you unwrapped the headlight wires........DUST poured out and the wires were bare copper touching each other.

Please don't do any more electrical work until you replace those wires. Many a GT has burned to the ground because of those wires shorting out.

:yikes:
 

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Opel Key Master
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AAAAAAAAAAAGGGGGGGGGHHHHHHH!

I almost coughed up my rectum when I read that. You're having electrical problems, you know your headlight wires are shot, and you're flipping your headlights.

AAAAAAAAAAAGGGGGGGGGHHHHHHH!

Okay, I did cough up my rectum that time.

I don't care if you buy a car with 10 miles on it, the FIRST thing you do to a GT is replace the headlight wires forward of the radiator wall. They are unfused. They are made of vinyl (they were rubber coated)which dried out and turned to dust after just 10 years. These are 50 year old cars. I had GT's in the early 80's that when you unwrapped the headlight wires........DUST poured out and the wires were bare copper touching each other.

Please don't do any more electrical work until you replace those wires. Many a GT has burned to the ground because of those wires shorting out.

:yikes:
I fixed your quote
 

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Opel Rallier since 1977
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2,220 Posts
Let's start with the resistance readings you report.... 2.2 ohms through the ammeter is definitely NOT OK. Even 0.22 ohms would be far too high for an ammeter. All your readings are quite high for wiring..... 2.5-3.2 ohm is abnormal, but it may be that the meter lead resistance is what you are really reading. If you short the lead together on you ohmmeter, what does it read?

Before going any further.... clean the battery terminals and connections thoroughly, and the ground connections.
 

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Discussion Starter #6
Thanks for the responses. After more looking at the wiring the headlights could be one of the issues. I'll jump the starter, recheck the key switch and start on the headlight wiring right away and report. I was using a Harbor Freight digital VOM and I found the positive test wire was bad. I'll recheck with my Simpson VOM and report. It is nice that so many want to help.
 

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Opel Rallier since 1977
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Awesome that you have a Simpson.. the old standard. Continuity is the best you can hope to measure through wiring of these gauges.

That 'muffled pop' was probably an arc as something burned through or separated, breaking the path. Do you have the schematics?
 

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Thanks for the responses. After more looking at the wiring the headlights could be one of the issues. I'll jump the starter, recheck the key switch and start on the headlight wiring right away and report. I was using a Harbor Freight digital VOM and I found the positive test wire was bad. I'll recheck with my Simpson VOM and report. It is nice that so many want to help.
My headlight wires were dust all the way back to the radiator wall but I went back to the firewall to replace mine, you only have 2 wires brights and normal brightness I made my cut there and soldered in new 12 gauge stranded wires there. On my 72’ they went to the electrical tape wrapped harness which made it easier to repair and re wrap. I had a 70’ once and it had a nice vinyl wrapped harness. I’d have a difficult time cutting in near the firewall to that nice vinyl cover. See what the condition of the wires are in front of the radiator wall and go from there. I put in line fuses for the 10 amp/yellow and 15 amp/white in front of the radiator to protect the new wires etc. Yep, those headlight wires are a guarantee for replacement. All the debris underneath the newly fused headlight wires came from the old wires to give you an idea. This picture was in front of the radiator wall.
 

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Discussion Starter #9
Thanks to everyone who took the time to consider my plight and offer input. I'm more of a jump first research later type of restorer. Oops! I never owned a GT beyond 1976 (it was a 71) and my last Opel was a 72 Manta Rallye so the headlight wiring never was an issue - I should have done my research first before the first smoke test. That said here is where we are:

The right headlight wiring did go to ground against part of the bucket assembly. Using a test box and voltage regulator I can say nothing on the dash got hurt. I can jump the starter and it cranks; With the ignition switch in run there is no power to the coil so no fire and there is no +12v at the black wire on the fuse block. There is battery +12v going into the fuse block at the red/white wire. What I don't know yet is if +12v is making it to the ignition switch or not going through. I'm going to make a test plug adapter to go between each plug and the fuse block so I can actively trace where and what.

I've got wiring diagrams from a factory service manual and from various on-line sources. I know what to do unless somebody can say definitively look at circuit wire "X" and that is rewire the headlamps and do a circuit by circuit check until I find what blew. On another car I installed a relay box and everything, fans, headlights, starter, etc. was switched through a relay - when I get the problem isolated I think I'll do that for this car because it looks light the ignition and other switches tote the entire current draw. It will be a while but I'll report as progress is made.

I'm still going to the Nationals, just probably sans Opel and hopefully I will get to meet ya'll and you will graciously allow me to pick your brains some more.

Later
 

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Just Some Dude in Jersey
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It's an honest mistake not knowing about the headlight wiring. Who would think that they used 2 different types of insulation. On top of that, they used that other type of insulator to PROTECT the wiring from shorting out as it passes through the rotator tubes. It turned out that it totally backfired on them and was the cause of more trouble than just about any other part of the car.

Another weak link is the ignition switch. They're very lightly and primitively built and all the engine/starter power flows through them. A recommended mod is to install a relay so that main power to the switch flows through the relay and only the power to energize the relay flows through the switch. Opel GT Source sells rebuilt ones if you determine that it's faulty.

The other main bugaboo when chasing electrical gremlins is the colored connectors on the fuse box and grounding at the various lights. You often need to freshen up the grounding connections. The plastic on the colored connectors has shrunk over time and the individual spade connectors push out of the both the male and female sides of the connectors and the fuse box, often cracked, also. You can trace many non-functioning gizmos to poorly connecting spade terminals.

Replacement fuse boxes from OGTS can be purchased, possibly wire harnesses, too. Or you can go aftermarket.

Keep up the good work!

:veryhappy
 

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Discussion Starter #11
Problem Solved

In a nutshell the ignition switch was smoked when the headlights shorted to ground. Nothing else was damaged - dumb luck, huh? I've rewired the headlights per OGTS instructions, bypassed the ignition switch with a spare ignition/start set from the parts bin, installed a relay in the start circuit, traced wires all over the place, cleaned up some weak grounds and she runs.

Working on these cars is like opening a 100lb bag of peanuts, you can't have just one and one always leads to another with no end in sight. Now about that cranky Solex carburetor, rebuild or Weber? Comments?
 

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Glad you were able to fix the problem and get your Opel running again. I would definitely go with a weber. I would surmise, most will chime in and say go with a weber.
Also, if you haven't, I would replace the ignition contact switch and turn signal ring. Most know the headlights are the primary concern, but then I have found the steering column to have electrical issues as well. In particular the turn signal ring wears and the ignition switch will burn out.

Good luck,

Dan
 
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